Publications

Lisa Marie Knowlton, MD, MPH, FACS, FRCSC
Associate Professor of Surgery (General Surgery)

Publications

  • Management of a traumatic splenic injury in the setting of polysubstance use and challenging social factors. Trauma surgery & acute care open Arbaugh, C. J., Brakebill, A., Spain, D. A., Knowlton, L. M. 2025; 10 (1): e001680

    View details for DOI 10.1136/tsaco-2024-001680

    View details for PubMedID 40041879

    View details for PubMedCentralID PMC11877270

  • Pre- and postinjury financial hardship among trauma survivors: A national survey study. The journal of trauma and acute care surgery Clark, N. M., Hernandez, A. H., Knowlton, L. M., Stewart, B. T., Bulger, E. M., Malloy, A., Anderson, G., Dieleman, J. L., Zatzick, D., Scott, J. W. 2025

    Abstract

    National estimates of financial hardship because of injury are lacking, which limits our ability to both define and mitigate the impacts of financial outcomes of trauma care. Furthermore, the absence of preinjury data limits our understanding of the association between injury and financial hardship.We analyzed data from the 2014-2021 Medical Expenditure Panel Survey. We compared injured adults (18-64 years old) to uninjured controls using coarsened-exact matching on age, sex, race/ethnicity, income, payer, survey panel, and comorbidities. Our main outcome of interest was financial hardship, a composite of difficulty paying medical bills, paying medical bills off over time, and delaying medical care because of cost. As a secondary analysis, we evaluated the link between difficulty paying medical bills, delaying care, and poor health.We included a weighted sample of more than 79 million injured patients over the 8-year study period. Difference-in-differences analysis using uninjured, matched controls showed that injured patients experienced an 8.2 percentage point increase in financial hardship (23% relative increase, with 40.6% reporting financial hardship postinjury, p < 0.001) and 4.5 percentage point increase in poor health (20% relative increase, p < 0.001). Injured patients who reported difficulty with medical bills were more likely to report delaying care because of costs (adjusted odds ratio, 3.3; 95% confidence interval, 2.5-4.4), and those who delayed care were more likely to report poor health (adjusted odds ratio, 1.5; 95% confidence interval, 1.2-2.0).In this national analysis of financial hardship before and after injury, 40% of injured patients reported difficulty with medical bills and delayed medical care because of cost. Programs aimed at disrupting the path from injury to financial hardship to poor long-term health have the potential to benefit millions of injury survivors.Retrospective Cohort Study; Level III.

    View details for DOI 10.1097/TA.0000000000004545

    View details for PubMedID 39910712

  • Awaiting insurance coverage: Medicaid enrollment and post-acute care use after traumatic injury. The journal of trauma and acute care surgery Haddad, D. N., Hatchimonji, J. S., Eisinger, E. C., Chen, A. T., Chreiman, K. M., Ramadan, O. I., Morgan, A. U., Delgado, M. K., Martin, N. D., Seamon, M. J., Knowlton, L. M., Kaufman, E. J. 2025

    Abstract

    Lack of insurance after traumatic injury is associated with decreased use of postacute care and poor outcomes. Insurance linkage programs enroll eligible patients in Medicaid at the time of an unplanned admission. We hypothesized that Medicaid enrollment would be associated with increased use of postacute care, but also with prolonged hospital length of stay (LOS) while awaiting insurance authorization.We linked trauma registry and EMR data to identify patients ages 18 years to 64 years admitted from 2017 to 2021 to a Level I trauma center. Patients admitted without insurance and retroactively insured (RI) during hospitalization were compared with patients with established Medicaid (MI) and those remaining uninsured (UI). We measured postacute care use including home health care, rehabilitation, and skilled nursing facilities. We tested the association between insurance status and discharge disposition and LOS (primary outcome) using multivariable negative binomial regression. Direct costs were compared between groups.We compared 494 RI patients to 1706 MI and 148 UI patients. Retroactively insured patients had longer hospitalization (median LOS [interquartile range], 4 days [2-9 days]) than other groups (MI, 4 [2-8] and UI 2 [1-3]), p < 0.001). Retroactively insured patients were more likely to be discharged with home health care and to inpatient rehabilitation than UI patients (p < 0.001). After adjusting for injury and management characteristics, RI was associated with longer LOS compared with MI for patients discharged to inpatient facilities (p < 0.001). Median costs for RI patients discharged to a facility were

  • Do emergency Medicaid programs improve post-discharge health care access for trauma patients? A statewide mixed-methods study. The journal of trauma and acute care surgery Knowlton, L. M., Arnow, K., Cosby, Z., Davis, K., Hendricks, W. D., Gibson, A. B., Chen, P., Morris, A. M., Wagner, T. H. 2024

    Abstract

    Hospital presumptive eligibility (HPE) emergency Medicaid programs offset patient bills at hospitalization and can provide long-term Medicaid coverage. We characterized postdischarge outpatient health care utilization among HPE Medicaid trauma patients and identified patient access facilitators and barriers once newly insured. We hypothesized utilization would be increased among HPE trauma patients compared with other HPE patients, but that challenges in access to care would remain.We performed a convergent mixed methods study of California HPE beneficiaries using a 2016 to 2021 customized statewide longitudinal claims dataset from the Department of Health Care Services. We compared adults 18 years and older with a diagnosis to other HPE patients. Patients were tracked for 2 months postdischarge to evaluate health care utilization: outpatient specialist visits, emergency room (ER) visits, readmissions, and mental health. Thematic analysis of semistructured interviews with HPE Medicaid patients aimed to understand facilitators and barriers to access to care (n = 20).Among 199,885 HPE patients, 39,677 (19.8%) had a primary diagnosis of trauma. In the 2 months postdischarge, 40.8% of trauma vs. 36.6% of nontrauma accessed outpatient specialist services; 18.6% vs. 17.2% returned to ED, 8.4% vs. 10.2% were readmitted; and 1.4% vs. 1.8% accessed mental health services. In adjusted analyses, trauma HPE patients had 1.18 increased odds of accessing outpatient specialist services (p < 0.01). Patients cited HPE facilitators to accessing care: rapid insurance acquisition, outpatient follow-up, hospital staff support, as well as ongoing barriers to access (HPE program information recall, lack of hospital staff follow up postdischarge, and difficulty navigating a complex health care system).Hospital presumptive eligibility Medicaid is associated with higher rates of outpatient specialist visits and fewer readmissions following injury, suggesting improved trauma patient access. Opportunities to improve appropriateness of health care utilization include more robust and longitudinal education and engagement with HPE Medicaid patients to help them navigate newfound access to services.Epidemiologic; Level II.

    View details for DOI 10.1097/TA.0000000000004519

    View details for PubMedID 39702232

  • Taking action to achieve health equity and eliminate healthcare disparities within acute care surgery. Trauma surgery & acute care open McCrum, M. L., Zakrison, T. L., Knowlton, L. M., Bruns, B., Kao, L. S., Joseph, K. A., Berry, C. 2024; 9 (1): e001494

    Abstract

    Addressing disparities is crucial for enhancing population health, ensuring health security, and fostering resilient health systems. Disparities in acute care surgery (trauma, emergency general surgery, and surgical critical care) have been well documented and the magnitude of inequities demand an intentional, organized, and effective response. As part of its commitment to achieve high-quality, equitable care in all aspects of acute care surgery, the American Association for the Surgery of Trauma convened an expert panel at its eigty-second annual meeting in September 2023 to discuss how to take action to work towards health equity in acute care surgery practice. The panel discussion framed contemporary disparities in the context of historic and political injustices, then identified targets for interventions and potential action items in health system structure, health policy, the surgical workforce, institutional operations and quality efforts. We offer a four-pronged approach to address health inequities: identify, reduce, eliminate, and heal disparities, with the goal of building a healthcare system that achieves equity and justice for all.

    View details for DOI 10.1136/tsaco-2024-001494

    View details for PubMedID 39416956

    View details for PubMedCentralID PMC11481130

  • Emergency Medicaid enrollment after traumatic injury predicts long-term health care utilization. The journal of trauma and acute care surgery Haddad, D. N., Eisinger, E., Hatchimonji, J. S., Chen, A. T., Ramadan, O. I., Morgan, A. U., Lile, D. J., Delgado, M. K., Reese, J., Seamon, M. J., Martin, N. D., Reilly, P. M., Knowlton, L. M., Kaufman, E. J. 2024

    Abstract

    Injured patients have high rates of uninsurance, which is associated with worse outcomes. Insurance linkage programs that connect patients to Medicaid coverage can prevent catastrophic costs for patients. Less is known about the long-term impact of insurance enrollment. We examined health care utilization for previously uninsured patients, hypothesizing that newly insured patients postinjury would use health care more than those remaining uninsured.We linked institutional trauma registry data to the electronic medical record to identify injured patients aged 18 to 64 years from 2017 to 2021. Patients admitted without insurance and then retroactively insured (RI) during hospitalization were compared with patients with preestablished Medicaid (Medicaid insured [MI]) and those remaining uninsured. We compared demographic and injury characteristics and future health care utilization, including hospitalizations, emergency department (ED) visits, and clinic visits, among groups at 30 days and 12 months postinjury. Patient-reported outcomes (PROs) 6 months after injury were compared by group for a subset of patients participating in an ongoing study of long-term PROs.We compared 494 RI patients with 1,706 MI and 148 uninsured patients. Retroactively insured patients were younger, more likely to have penetrating injuries, and longer hospitalization than other groups. There was a significant increase in ED and clinic visits and hospital admissions at 30 days and 12 months between RI and uninsured patients (p < 0.001). Using multivariable logistic regression, RI was associated with higher future ED utilization, hospital admissions, and specialist visits at 30 days and 12 months compared with uninsured patients. Of the 265 patients with 6-month PROs, Medicaid coverage was not associated with any significant difference in physical function or anxiety.Patients enrolled in insurance postinjury are more likely to use health care in the future than patients without insurance, but the downstream effects are less clear. Health insurance is a necessary step but not independently sufficient to optimize care and improve health outcomes.Prognostic and Epidemiological; Level IV.

    View details for DOI 10.1097/TA.0000000000004403

    View details for PubMedID 39225808

  • Does preperitoneal packing increase venous thromboembolim risk among trauma patients? A prospective multicenter analysis across 17 level I trauma centers. The journal of trauma and acute care surgery Knowlton, L. M., Sauaia, A., Moore, E. E., Knudson, M. M., CLOTT Study Group 2024

    Abstract

    INTRODUCTION: Pelvic fractures are associated with a high risk of venous thromboembolism (VTE). Among treatment options, including pelvic angioembolization (PA), preperitoneal pelvic packing (PPP), and pelvic open reduction internal fixation (ORIF), PPP has been postulated as a VTE risk factor. We aimed to characterize the risk of VTE among pelvic fracture patients receiving PPP, PA or ORIF.METHODS: We used observational data from a 17-site Consortium of Leaders in the Study of Traumatic Thromboembolism (CLOTT) study group, a US level I trauma center collaborative working to identify factors associated with posttraumatic VTE, deep venous thrombosis, pulmonary embolism, or pulmonary thrombosis. The CLOTT criteria included age 18 to 40 years with at least one independent VTE risk factor. We compared outcomes of PPP, PA, and pelvic ORIF to reference of no pelvic intervention. Our primary outcome was VTE. A competing risk analysis was performed.RESULTS: Among 1,387 pelvic fracture patients, VTE incidence was 5.6%. The ORIF patients were most likely to develop VTE (24.7%), while VTE incidence for PPP was 9.0% and 2.6% for PA. After multivariate, risk-competing analysis, none of the three treatment interventions for pelvic fractures were significantly associated with VTE. Initiation of VTE prophylaxis in the first 24 hours of admission independently halved VTE incidence (hazard ratio, 0.55; confidence interval, 0.33-0.91).CONCLUSION: Pelvic fracture interventions do not appear to be independent risk factors for VTE in our study. Initiation of VTE pharmacoprophylaxis within the first 24 hours of admission remains critical to significantly decreasing VTE formation in this high-risk population.LEVEL OF EVIDENCE: Therapeutic Study; Level III.

    View details for DOI 10.1097/TA.0000000000004416

    View details for PubMedID 39058389

  • Hospital Presumptive Eligibility Emergency Medicaid Programs: An Opportunity for Continuous Insurance Coverage? Medical care Knowlton, L. M., Arnow, K., Trickey, A. W., Tran, L. D., Harris, A. H., Morris, A. M., Wagner, T. H. 2024

    Abstract

    Lack of health insurance is a public health crisis, leading to foregone care and financial strain. Hospital Presumptive Eligibility (HPE) is a hospital-based emergency Medicaid program that provides temporary (up to 60 d) coverage, with the goal that hospitals will assist patients in applying for ongoing Medicaid coverage. It is unclear whether HPE is associated with successful longer-term Medicaid enrollment.To characterize Medicaid enrollment 6 months after initiation of HPE and determine sociodemographic, clinical, and geographic factors associated with Medicaid enrollment.This was a cohort study of all HPE approved inpatients in California, using claims data from the California Department of Healthcare Services.The study was conducted across all HPE-participating hospitals within California between January 1, 2016 and December 31, 2017.We studied California adult hospitalized inpatients, who were uninsured at the time of hospitalization and approved for HPE emergency Medicaid. Using multivariable logistic regression models, we compared HPE-approved patients who enrolled in Medicaid by 6 months versus those who did not.HPE emergency Medicaid approval at the time of hospitalization.The primary outcome was full-scope Medicaid enrollment by 6 months after the hospital's presumptive eligibility approval.Among 71,335 inpatient HPE recipients, a total of 45,817 (64.2%) enrolled in Medicaid by 6 months. There was variability in Medicaid enrollment across counties in California (33%-100%). In adjusted analyses, Spanish-preferred-language patients were less likely to enrollin Medicaid (aOR 0.77, P<0.001). Surgical intervention (aOR 1.10, P<0.001) and discharge to another inpatient facility or a long-term care facility increased the odds of Medicaid enrollment (vs. routine discharge home: aOR 2.24 and aOR 1.96, P<0.001).California patients who enroll in HPE often enroll in Medicaid coverage by 6 months, particularly among patients requiring surgical intervention, repeated health care visits, and ongoing access to care. Future opportunities include prospective evaluation of HPE recipients to understand the impact that Medicaid enrollment has on health care utilization and financial solvency.

    View details for DOI 10.1097/MLR.0000000000002026

    View details for PubMedID 38986116

  • Small bowel obstruction due to a migrated pyloric stent. Trauma surgery & acute care open Agolia, J. P., Wang, S., Fisher, A., Bryan, J. L., Knowlton, L. M. 2024; 9 (1): e001443

    View details for DOI 10.1136/tsaco-2024-001443

    View details for PubMedID 38756695

    View details for PubMedCentralID PMC11097799

  • Value in Acute Care Surgery, Part 3: Defining Value in Acute Surgical Care - It Depends on the Perspective. The journal of trauma and acute care surgery Ayoung-Chee, P. R., Gore, A. V., Bruns, B., Knowlton, L. M., Nahmias, J., Davis, K. A., Leichtle, S., Ross, S. W., Scherer, L. R., Velopulos, C., Martin, R. S., Staudenmayer, K. L. 2024

    Abstract

    The prior articles in this series have focused on measuring cost and quality in acute care surgery. This third article in the series explains the current ways of defining value in acute care surgery, based on different stakeholders in the healthcare system - the patient, the healthcare organization, the payer and society. The heterogenous valuations of the different stakeholders require that the framework for determining high-value care in acute care surgery incorporates all viewpoints.

    View details for DOI 10.1097/TA.0000000000004347

    View details for PubMedID 38706096